Defecate not where you dine.
Non-political:
Queuing up / lining up (in the US), don’t cut in line. Nobody really needs to be told to do this in most public circumstances.
Drive on the right, don’t run red lights, don’t drink and drive. While these are underpinned by laws, they are also in the realm of widely agreed upon common sense.
“Common sense” is the consideration of the potential consequences of your acts.
Things you can’t justify except through recourse to common sense.
In other words, they’re either commonsensical or nonsensical.
For example: Women belong in the kitchen. That’s bedrock common sense for some people, and utterly foreign to others. Women working outside the home when they’re married is anathema to people of some backgrounds, but ask them to justify that feeling and they’re left with two things: Appeal to precisely the premise you just rejected (as in, it’s wrong because it’s wrong) or a swift kick in the ass, because they’re going to win, dammit, and if you’re too insane to see reason they have to resort to force.
Another example: Their chosen religious group has the right to dictate morality without being questioned. A number of them define morality as being what their religion says is right, therefore, if you’re a moral person, you’re already a member of their chosen sect even if you’re playing silly buggers by claiming otherwise right now. (Conversely, they may conclude that if you’re not a member, you’re utterly amoral, and therefore immoral, and therefore a murder-rapist.) They might have rationalizations for specific pronouncements, arguments they can trot out when someone questions a specific thing their religious group has ruled on, but those barely qualify as “arguments” and are laughably weak unless you already agree with them, in which case your entire moral worldview is predisposed to accept them and disagreeing would be perverse.
I have to respond to this: “Common sense” includes a sense of what those consequences will be.
It’s the old wheeze: “Freedom of speech doesn’t include freedom from consequences.” Well, ask the next question: “Who gets to decide what the consequences are going to be?”
Common sense is usually a concept like minded people agree upon.
or slim later on 
This, basically. It’s poisoning the well; preventing people from being able to disagree.
A pamphlet by Thomas Paine.
Merriam-Webster gives a basic definition of “sound and prudent judgment based on a simple perception of the situation or facts”, but this definition points out the flaw in using “common sense”-Can “sound and prudent judgment” be accurately derived from a “simple perception of the situation or facts”? I think that further examination of a situation must be done before anything approaching a “sound and prudent judgment” can be made.
Common sense is what tells you that the earth is flat.
My definition of common sense is knowledge that so fundamental it isn’t taught but rather arrived at through the most basic of life experiences.
Examples:
- When you constantly attack someone personally, that person will usually consider you an enemy.
- Eating a lot of junk food and not exercising will eventually make you gain weight.
- Throwing rocks at a lion and not running away when the lion charges is a good way to get killed by a lion.
- You can improve your chances of getting a mate by making an effort to be pleasant and look attractive.
- Metal becomes hot when sitting in a fire, so you will get burned if your reach into the fire and grab it. And also, fire will burn you too.
To be honest, I’ve never understood what isn’t clear about “common sense” as its typically used. Would anyone argue that the above examples are something the vast majority of people shouldn’t know? To me, failures in common sense give rise to what we commonly refer to as the Darwin awards.
In this context, “common sense” is what your people feel is true. It’s a standard by which to judge if someone is “normal” or an outsider. It is by definition divisive. Abortion, climate change, etc absolutely fall under the category of “common sense” - to half of Americans anyway.
Yes it most certainly can.
Simple perceptions: The house is on fire. You are trapped in a ground-floor bedroom. Flames are blazing in the hallway. Everyone in your family (including pets) have made it out except you, and you know this, because you see them outside. There is a window (no burglar bars) in your room that is big enough for you to squeeze through.
Sound and prudent judgment (AKA common sense): Exit the house through the window.
Unsound and imprudent judgment (no common sense):
- wrap yourself in a wool blanket and run into the hallway, or
- stay in the room, even as the fire spreads inside, or
- kick a hole in the wall in the hopes you can squeeze your way out of it
This squares with a definition I happen to like, in fact: “Common sense is the collection of prejudices acquired by age eighteen.” – Most likely Albert Einstein
I agree with your examples. What I don’t agree with is following them up with “… and therefore you can’t get married” or “… and therefore people like you can’t work here” or some other topic their resolution to which probably does seem commonsensical to them, but which is a topic on which reasonable people can disagree.
Because, as others have said, claiming a topic is simple and the conclusion is common sense forecloses on disagreement. It’s breathtakingly dishonest and the only reason anyone gets away with it is because they’re in a position of power such that others think they can dictate common sense, or they’re surrounded by like-minded people who have no reason to see the dishonesty.
That, or they’re what Shaw called “barbarians”: People who think the customs of their tribe and island are laws of nature. (George Bernard Shaw, Caesar and Cleopatra)
The farther removed consequences are from nature, then less common sensical they are. Because remember, they aren’t consequences that are taught per se, but inferred from a very basic understanding of how the world works. So while I agree that it’s problematic when people extend judgments to the things you’ve pointed out, I disagree this makes the common sense concept inherently problematic.
That’s one way to look at it. Another view is that by encouraging people to use common sense, what you’re actually asking people to do is reason through problems.
Imagine this conversation.
Mother: You’re soaking wet, Billy! Why did you get caught out in the rain without an umbrella again?
Billy: Because the weatherman said it was going to be sunny today.
Mother: But it was raining when you left the house. Didn’t you realize you’d need your umbrella just by looking out the window?
Billy: Yes, but the weatherman said it was going to be sunny today. So I figured it would soon stop.
Mother: Obviously he was wrong. When did you hear this forecast?
Billy: Last week.
We all know someone like Billy. On the surface, they are as smart as anyone else. But when it comes to thinking things through logically, they totally abdicate the thrown. This makes them suspectible to misinformation and the influence of other stupid people.
To go back to the OP, Trump speaks in simple phrases with a pre-school vocabulary. Because he uses basic words to express himself, it makes it seem like he’s speaking “common sensical” truths to people who themselves are lacking in common sense.
I like that definition.
Ah, but there are places where the most common system involves, not physical lines, but asking “who’s last”. This allows people to leave the queue to do other stuff knowing their spot will be kept so long as they return before their turn comes up (if you miss it tough titty, you have to ask “who’s last” again); it also allows those who are in worse physical shape or simply more tired to take advantage of lean-tos or seats nearby, again without losing their spot.
To me that’s perfectly logical and instinctive because it’s part of the customs I learned since childhood. To someone from a queuing country, it’s a bloody mess.